As advances in semiconductor technology reduce the feature sizes of the devices, integrated circuit density increases. This high density of devices requires closely spaced metal lines in low-dielectric constant (low-k) insulators to interconnect these closely spaced devices. A low-k insulator is advantageous to reduce the capacitance between the closely spaced metal lines, thereby reducing the RC time constant in the metal lines and improving circuit performance.
One of the problems associated with using a low-k insulator is photoresist poisoning or contamination during processing. For example, when photoresist is used directly on low-k insulators, photoresist poisoning can occur. One known method is to use a SiON liner in contact openings in the low-k insulator to minimize the photoresist poisoning. However, these SiON liners are not completely effective.